1. Technical Field
The present invention generally pertains to an automatic transmission for a motor vehicle. More specifically, but without restriction to the particular embodiment or use which is shown and described for purposes of illustration, the present invention relates to a method for reacting thrust loading of a planetary gear system in the automatic transmission.
2. Description of the Related Art
A conventional automatic transmission includes a hydrodynamic torque converter to transfer engine torque from an engine crank shaft to a rotatable input member of the transmission through fluid-flow forces. The transmission also includes frictional units, typically referred to as clutches or brakes, which couple the rotatable input member to a member of a planetary gear assembly or hold a member of the planetary gear set stationary during the transmission of power. Such automatic transmissions typically provide for multiple planetary gear sets in order to provide various ratios of torque and to ensure that the available torque and the respective tractive power demand are matched.
In an effort to further optimize the automatic transmission and minimize the weight thereof, various components which were previously fabricated from steel are being fabricated from lighter weight materials such as aluminum. While the use of such materials can significantly reduce the weight of components within the transmission, these components do not possess the same strength of materials properties as steel. As such, components made from alternate materials may be incapable of supporting and reacting certain internal loads generating during extreme operating conditions.
As an example, significant axial or thrust loads are generated by the various planetary gear sets during the operation of the automatic transmission. These thrust loads are transmitted and reacted through various components, such as the oil pump, in the automatic transmission. The continuous normal-use loading, as well as certain extreme operating conditions, such as the full torque converter stall condition, may be sufficient to ultimately result in failure of such components.